Commercially available display devices include: a mobile terminal-use display capable of directly or indirectly controlling a detection (reception) device having a touch panel function; and a mobile terminal equipped with such a mobile terminal-use display.
The detection device includes a detection section for detecting a touch of a human finger or stylus. A human finger or stylus traces the detection section (touches the detection section). Consequently, a user's operation of a mobile terminal, corresponding to the tracing movement (touching movement), is detected by the detection section.
The above-mentioned mobile terminal-use display (display device) equipped with a touch panel generates noises when it carries out scanning. The noises influence the touch panel (capacitive touch panel in particular), thus deteriorating detection accuracy of the touch panel (detection device).
In order to deal with this, as shown in a first conventional art example in FIG. 16, there has been conventionally performed a control to synchronize a non-scanning period (blanking period) during which a moving image is not displayed on the display device with a detection period (touch panel detection period) of the detection device. Synchronization of the non-scanning period and the detection period allows greatly improving detection accuracy.
The control performed in the first conventional art example in FIG. 16 suffers a problem below. Since the non-scanning period (blanking period) is normally on the order of 100 μsec, the detection period synchronized with the non-scanning period is also on the order of 100 μsec. Normally, the detection period requires approximately 10 msec. Accordingly, the control performed in the first conventional art example does not allow the detection device to make detection.
In order to deal with the problem of the first conventional art example in FIG. 16, a control performed in a second conventional art example in FIG. 17 has been proposed. As shown in FIG. 17, the second conventional art example makes a scanning period as short as possible, thereby making a non-scanning period as long as possible (e.g. 0.5 msec or more). The non-scanning period is synchronized with the detection period, similarly with the first conventional art example.
In the control performed in the second conventional art example, the non-scanning period is synchronized with the detection period, similarly with the first conventional art example. Therefore, the control performed in the second conventional art example can greatly improve accuracy in detection, similarly with the first conventional art example.
In addition, in the control performed in the second conventional art example, the non-scanning period is made longer, so that the detection period is made longer, too. This allows securing a detection period required for detecting user's operation.
The control performed in the second conventional art example in FIG. 17 suffers a problem below. In the control performed in the second conventional art example, one frame period includes one scanning period and one non-scanning period, similarly with the control performed in the first conventional art example. The non-scanning period is synchronized with the detection period.
Therefore, the number of the scanning periods is equal to the number of the non-scanning periods (i.e. the number of times detection is made). Accordingly, a detection frequency offered by a touch panel which serves as a detection device is equal to a refresh frequency of a display device.
In the control performed in the second conventional art example in FIG. 17, since one frame period is 16.6 msec, a refresh frequency of the display device is 60 Hz. In this case, a detection frequency offered by the touch panel which serves as the detection device is also 60 Hz. Therefore, the control performed in the second conventional art example cannot deal with handwriting which requires a detection frequency of 100 Hz or more.
In relation to the second conventional art example in which the non-scanning period is made as long as possible, Patent Literature 1 discloses a method for driving a display device that provides a non-scanning period which is longer than a scanning period during which scanning is carried out once over the screen. This driving method provides a pause period during which all scanning signal lines are brought into a non-scanning state, thereby realizing low power consumption.